Field of the Invention
The present invention relates to an image sensor, an image capturing apparatus, and a method for controlling the image capturing apparatus.
Description of the Related Art
It is known that a phase difference AF (Auto Focus) function can be realized by arranging, on an image capturing sensor, phase-difference detecting pixels that are capable of photoelectrically converting a part of a light flux passing through a microlens and outputting it.
In order to realize the phase difference AF function using the image capturing sensor, pixels that generate phase-difference detecting signals necessary for phase difference AF are required to be identified. Japanese Patent Laid-Open No. 2012-120158 discloses that information identifying phase-difference detecting pixels and image forming pixels is added to the payload in which pixel data equivalent to a single line of the image sensor is stored, and a DSP identifies whether the pixel data serves to detect a phase difference or to form an image by referring to the information.
As disclosed in Japanese Patent Laid-Open No. 2012-120158, the processing efficiency for the phase difference AF function can be increased by adding signals for determining whether the pixel data represents phase-difference detecting pixels or image forming pixels.
However, output signals of phase-difference detecting pixels may possibly be optically affected by the light flux reaching an imaging plane and affected by electrical properties specific to the phase-difference detecting pixels. Therefore, in order to realize the phase difference AF function, it is necessary to correct a plurality of adjustment parameters such as the positional relationship on the image sensor, the offset, and the amount of gain. Generally, such a plurality of adjustment parameters are sequentially corrected by a plurality of circuit blocks corresponding to the respective parameters. Therefore, a control unit of an image capturing apparatus controls processes of the respective blocks individually, and completes the correction processing as a whole. Since responses of the respective circuit blocks to the control unit may possibly be asynchronous depending on contents of the processes, the processing flow and the state transition tend to be complex, and the processing load on the control unit tends to increase.